The film adaptation of American Psycho, Bret Easton Ellis’ satire on 1980s materialism, has solidified itself in pop culture, inspiring dozens of parodies and thousands of Halloween costumes, much to Ellis’ disdain. The movie is celebrating its 15th anniversary, so to mark such a bloody occasion, here are some facts you might not know about the high-rolling, murderous life of Patrick Bateman. Starting with how Willem Dafoe attempted to confuse the hell out of the audience.

1. Willem Dafoe shot each of his scenes three different ways. In order to create some mystery about how much Detective Kimball knew about Patrick Bateman, Dafoe acted out each of his scenes in three different ways. Dafoe would say his lines under the premise that his character knew that Bateman killed Paul Allen, then like his character didn’t know he killed him, and finally, as if his character was unsure if Bateman was involved with Paul Allen’s disappearance. The various scenes were then edited to together to give the audience an unsure feeling of how much Detective Kimball really knew.

2. The movie was originally going to be in black and white and rated X. Ellis’ novel was getting the attention of Hollywood as far back as 1991, when it was slated to be directed by Stuart Gordon (Re-Animator). Gordon had tapped young heart-throb Johnny Depp to star as Bateman and planned to shoot the movie in black and white and stick as close to the book’s graphic violence as possible. This would have meant the dreaded X-rating, and the project fell through. It bounced around to David Cronenberg with Brad Pitt starring before eventually landing at Lions Gate with Mary Harron directing.

3. Ellis didn’t care for Bale’s dancing. Just before Bateman puts an ax in Paul Allen’s head, he dances to along to “Hip to Be Square” by Huey Lewis and the News. This was improvised by Christian Bale, and while Mary Harron thought it was hysterical, Bret Easton Ellis didn’t like it.

4. Bateman becomes Batman.Guinevere Turner played the role of Elizabeth and wrote the screenplay for the film, ultimately beating three other scripts, including one written by Bret Easton Ellis. In the movie, Elizabeth dubs Patrick with the nickname of Batman by removing the letter “E” from his last name. Of course, Bateman would become Batman five years later when Christian Bale signed on for Batman Begins.

5. Ellis thought the movie botched the story’s ending. Authors are often the toughest critics of film adaptations of their work, and Ellis took issue with the movie’s ending. He said that by adapting the book to film, certain questions must be answered, like whether Patrick Bateman really hacked all those people to bits, or if it was all in his head.

What questions do you think she [Mary Harron] answered that she shouldn’t have? Whether or not this was all in Patrick Bateman’s head?

Right. And a movie automatically says, “It’s real.” Then, at the end, it tries to have it both ways by suggesting that it wasn’t. Which you could argue is interesting, but I think it basically confused a lot of people, and I think even Mary would admit that.

6. Tom Cruise provided some of the inspiration for Patrick Bateman. Bale drew some of his inspiration for Bateman’s character from one of Hollywood’s biggest stars at the time, Tom Cruise. Director Mary Harron recalled that Bale had seen Cruise in an interview with David Letterman and thought there was nothing behind his eyes that would fit well with Bateman.

“It was definitely a process. [Bale and I] talked a lot, but he was in L.A. and I was in New York. We didn’t actually meet in person a lot, just talked on the phone. We talked about how Martian-like Patrick Bateman was, how he was looking at the world like somebody from another planet, watching what people did and trying to work out the right way to behave. And then one day he called me and he had been watching Tom Cruise on David Letterman, and he just had this very intense friendliness with nothing behind the eyes, and he was really taken with this energy.”